Reassembly of somatic cells and testicular organogenesis in vitro

In vitro spermatogenesis in artificial testis: current knowledge and clinical implications for male infertility

Men's reproductive health exclusively depends on the appropriate maturation of certain germ cells known as sperm. Certain illnesses, such as Klinefelter syndrome, cryptorchidism, and syndrome of androgen insensitivity or absence of testis maturation in men, resulting in the loss of germ cells and the removal of essential genes on the Y chromosome, can cause non-obstructive azoospermia. According to laboratory research, preserving, proliferating, differentiating, and transplanting spermatogonial stem cells or testicular tissue could be future methods for preserving the fertility of children with cancer and men with azoospermia. Therefore, new advances in stem cell research may lead to promising therapies for treating male infertility. The rate of progression and breakthrough in the area of in vitro spermatogenesis is lower than that of SSC transplantation, but newer methods are also being developed. In this regard, tissue and cell culture, supplements, and 3D scaffolds have opened new horizons in the differentiation of stem cells in vitro, which could improve the outcomes of male infertility. Various 3D methods have been developed to produce cellular aggregates and mimic the organization and function of the testis. The production of an artificial reproductive organ that supports SSCs differentiation will certainly be a main step in male infertility treatment.

In Vitro and In Vivo Models for Drug Transport Across the Blood-Testis Barrier

The blood-testis barrier (BTB) is a selectively permeable membrane barrier formed by adjacent Sertoli cells (SCs) in the seminiferous tubules of the testes that develops intercellular junctional complexes to protect developing germ cells from external pressures. However, due to this inherent defense mechanism, the seminiferous tubule lumen can act as a pharmacological sanctuary site for latent viruses (e.g., Ebola, Zika) and cancers (e.g., leukemia). Therefore, it is critical to identify and evaluate BTB carrier-mediated drug delivery pathways to successfully treat these viruses and cancers. Many drugs are unable to effectively cross cell membranes without assistance from carrier proteins like transporters because they are large, polar, and often carry a charge at physiologic pH. SCs express transporters that selectively permit endogenous compounds, such as carnitine or nucleosides, across the BTB to support normal physiologic activity, although reproductive toxicants can also use these pathways, thereby circumventing the BTB. Certain xenobiotics, including select cancer therapeutics, antivirals, contraceptives, and environmental toxicants, are known to accumulate within the male genital tract and cause testicular toxicity; however, the transport pathways by which these compounds circumvent the BTB are largely unknown. Consequently, there is a need to identify the clinically relevant BTB transport pathways in in vitro and in vivo BTB models that recapitulate human pharmacokinetics and pharmacodynamics for these xenobiotics. This review summarizes the various in vitro and in vivo models of the BTB reported in the literature and highlights the strengths and weaknesses of certain models for drug disposition studies. SIGNIFICANCE STATEMENT: Drug disposition to the testes is influenced by the physical, physiological, and immunological components of the blood-testis barrier (BTB). But many compounds are known to cross the BTB by transporters, resulting in pharmacological and/or toxicological effects in the testes. Therefore, models that assess drug transport across the human BTB must adequately account for these confounding factors. This review identifies and discusses the benefits and limitations of various in vitro and in vivo BTB models for preclinical drug disposition studies.

Differentiation and proliferation of spermatogonial stem cells using a three-dimensional decellularized testicular scaffold: a new method to study the testicular microenvironment in vitro

PURPOSE

Successful in vitro transplantation of spermatogonial stem cells (SSCs) demands effective culture systems for SSCs proliferation and differentiation. Natural extracellular matrix (ECM) creates a microenvironment suitable for culture of stem cells. In the present study, we intended to assess the capability of the porous scaffold consisting of hyaluronic acid (HA), chitosan, and decellularized testicular matrix (DTM) as a proper niche for SSCs seeding.

METHODS

The testes of four NMRI mice were extracted for further detergent-based decellularization process. We isolated, cultured, and clarified neonate mouse SSC, and a three-dimensional scaffold was prepared for SSCs culture. The loaded SSCs and hydrogel-based scaffold were investigated by several studies including scanning electron microscopy (SEM), 4',6-diamidino-2-phenylindole (DAPI), 3-[4, 5-dimethyl (thiazol-2yl)-3,5diphenyl] tetrazolium bromide (MTT), Acridine orange, and Immunohistochemistry (IHC) staining.

RESULTS

The efficiency of decellularization process was confirmed by DAPI, hematoxylin and eosin (H&E), and Masson's Trichrome staining. Acridine orange also depicted SSCs proliferation and viability. SEM approved the preservation of ECM components and also showed complex, coiled, and tubular seminiferous tubules, with intact and condensed collagenous form of the tunica albuginea. MTT test also revealed the scaffold's non-toxicity. Expression of PLZF, TP1, and TEKT1 markers also verified the capacity of SSCs proliferation on a cogel scaffold.

CONCLUSION

In conclusion, cogel scaffold consisting of DTM, HA, and chitosan may provide the supporting layer for in vitro SSC differentiation and proliferation.

Current progress, challenges, and future prospects of testis organoids†

Spermatogenic failure is believed to be a major cause of male infertility. The establishment of a testis organoid model would facilitate the study of such pathological mechanisms and open the possibility of male fertility preservation. Because of the complex structures and cellular events occurring within the testis, the establishment of a compartmentalized testis organoid with a complete spermatogenic cycle remains a challenge in all species. Since the late 20th century, a great variety of scaffold-based and scaffold-free testis cell culture systems have been established to recapitulate de novo testis organogenesis and in vitro spermatogenesis. The utilization of the hydrogel scaffolds provides a 3D microenvironment for testis cell growth and development, facilitating the reconstruction of de novo testis tissue-like structures and spermatogenic differentiation. Using a combination of different strategies, including the use of various scaffolding biomaterials, the incorporation of the living cells with high self-assembling capacity, and the integration of the advanced fabrication techniques, a scaffold-based testis organoid with a compartmentalized structure that supports in vitro spermatogenesis may be achieved. This article briefly reviews the current progress in the development of scaffold-based testis organoids while focusing on the scaffolding biomaterials (hydrogels), cell sources, and scaffolding approaches. Key challenges in current organoid studies are also discussed along with recommendations for future research.

Advanced bioengineering of male germ stem cells to preserve fertility

In modern life, several factors such as genetics, exposure to toxins, and aging have resulted in significant levels of male infertility, estimated to be approximately 18% worldwide. In response, substantial progress has been made to improve in vitro fertilization treatments (e.g. microsurgical testicular sperm extraction (m-TESE), intra-cytoplasmic sperm injection (ICSI), and round spermatid injection (ROSI)). Mimicking the structure of testicular natural extracellular matrices (ECM) outside of the body is one clear route toward complete in vitro spermatogenesis and male fertility preservation. Here, a new wave of technological innovations is underway applying regenerative medicine strategies to cell-tissue culture on natural or synthetic scaffolds supplemented with bioactive factors. The emergence of advanced bioengineered systems suggests new hope for male fertility preservation through development of functional male germ cells. To date, few studies aimed at in vitro spermatogenesis have resulted in relevant numbers of mature gametes. However, a substantial body of knowledge on conditions that are required to maintain and mature male germ cells in vitro is now in place. This review focuses on advanced bioengineering methods such as microfluidic systems, bio-fabricated scaffolds, and 3D organ culture applied to the germline for fertility preservation through in vitro spermatogenesis.

Recellularization of testicular feminization testis in C57bl6 as a natural bioreactor for creation of cellularized seminiferous tubules: an experimental study

We determined histological aspects of implanted human decellularized testicular matrix (DTM) in C57BL6 as a primitive step for further testis tissue engineering. A total of 4 immature human testicles were obtained after bilateral orchiectomy from patients with testicular feminization syndrome. The optimal decellularization protocol was determined and the efficacy of decellularization was evaluated in two of the testicles. The remaining scaffolds were cut in 3 × 3 mm³ pieces and implanted between the tight muscles in 32 C57BL6. Biopsies were taken at 2, 4, 8, and 24 weeks postoperatively and stained with PLZF, protamine, and tekt1 markers. Histological examination of DTMs confirmed complete absence of nuclear remnants and preservation of the extracellular matrix. Successful cell seeding was observed in all follow-ups confirmed by H&E and IHC staining that increased continuously during the whole study. Interestingly, spermatogonial stem-like cells were observed on decellularized implants that were well differentiated during the follow-ups. Natural bioreactors may provide a good cell source for testes tissue regeneration. This technique may provide testis bioscaffold as a three-dimensional platform and further successful cell seeding to produce a functional testis. This novel technique may be beneficial for patients who require testicular supplementation.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Challenging human somatic testicular cell reassembly by protein kinase inhibition -setting up a functional in vitro test system

Signalling pathways and cellular interactions defining initial processes of testis morphogenesis, i.e. cord formation, are poorly understood. In vitro cell-based systems modelling cord formation can be utilised as platforms to interrogate processes of tubulogenesis. We aimed at testing our established cord formation in vitro model using adult human testicular cells as a quantitative assay that can facilitate future studies on cord morphogenesis. We challenged the responsiveness of our system with a broad-spectrum protein kinase inhibitor, K252a. Cultured testicular cells were treated with various K252a concentrations under constant exposure and compound withdrawal. To quantify cell reaggregation changes, we performed computer-assisted phase-contrast image analysis of aggregate size and number. Cell reaggregation was analysed in detail by categorisation of aggregates into size groups and accounting for changes in aggregate number per size category. We found a dose-related disturbance of testicular cell reaggregation. K252a decreased aggregate size (IC50 of 203.3 nM) and reduced the large aggregate numbers. Video recordings revealed that treatment with K252a at a concentration above IC50 interfered with aggregate coalescence into cords. Short-term exposure and compound wash-out induced irreversible decrease in large aggregates. We propose our in vitro model as a functional platform to quantitatively investigate seminiferous tubulogenesis under pharmacological impact.

In-vitro spermatogenesis through testis modelling: Toward the generation of testicular organoids

Background

The testicular organoid concept has recently been introduced in tissue engineering to refer to testicular cell organizations modeling testicular architecture and function. The testicular organoid approach gives control over which and how cells reaggregate, which is not possible in organotypic cultures, thereby extending the applicability of in‐vitro spermatogenesis (IVS) systems. However, it remains unclear which culture method and medium allow reassociation of testicular cells into a functional testicular surrogate in‐vitro.

Objective

The aim of this paper is to review the different strategies that have been used in an attempt to create testicular organoids and generate spermatozoa. We want to provide an up‐to‐date list on culture methodologies and media compositions that have been used and determine their role in regulating tubulogenesis and differentiation of testicular cells.

Search method

A literature search was conducted in PubMed, Web of Science, and Scopus to select studies reporting the reorganization of testicular cell suspensions in‐vitro, using the keywords: three‐dimensional culture, in‐vitro spermatogenesis, testicular organoid, testicular scaffold, and tubulogenesis. Papers published before the August 1, 2019, were selected.

Outcome

Only a limited number of studies have concentrated on recreating the testicular architecture in‐vitro. While some advances have been made in the testicular organoid research in terms of cellular reorganization, none of the described culture systems is adequate for the reproduction of both the testicular architecture and IVS.

Conclusion

Further improvements in culture methodology and medium composition have to be made before being able to provide both testicular tubulogenesis and spermatogenesis in‐vitro.

Rebuilding the human testis in vitro

Increasing rates of male infertility have led to a greater need for relevant model systems to gain further insight into male fertility and its failings. Spermatogenesis and hormone production occur within distinct regions of the testis. Defined by specialized architecture and a diverse population of cell types, it is no surprise that disruption of this highly organized microenvironment can lead to infertility. To date, no robust in vitro system has facilitated full spermatogenesis resulting in the production of fertilization‐competent human spermatozoa. Here, we review a selection of current in vitro systems available for modelling the human testis microenvironment with focus on the progression of spermatogenesis and recapitulation of the testis microenvironment.

Dynamics, ultrastructure and gene expression of human in vitro organized testis cells from testicular sperm extraction biopsies

STUDY QUESTION

Is it possible to induce in vitro reorganization of primary human testis cells from testicular sperm extraction (TESE) biopsies, maintain their long-term cultivation in a 2D system and identify cellular compositions?

SUMMARY ANSWER

In vitro reorganization of primary human testis cells from TESE biopsies and their long-term cultivation on uncoated cell culture dishes is feasible and the cellular compositions can be uncovered through gene expression and microscopic analyses.

WHAT IS KNOWN ALREADY

It has been shown in the rodent model that mixtures of testicular cell types are able to reassemble into clusters when cultivated on different kinds of surfaces or three-dimensional matrices. Two recent publications demonstrated the ability of primary human testicular cells to assemble into testicular organoids and their cultivation for a period of 3-4 weeks.

STUDY DESIGN SIZE, DURATION

Primary human testis cells from TESE biopsies from 16 patients were reorganized in vitro and the clusters were cultivated long term on uncoated cell culture dishes, providing a solid ground for in vitro spermatogenesis. Gene expression analysis as well as fluorescence/transmission electron microscopy (TEM) were employed to uncover the cellular composition of the clusters.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Testis biopsies from adult, normogonadotropic patients displaying full spermatogenesis (n = 11), hypospermatogenesis (n = 2), predominantly full spermatogenesis with some hypospermatogenic tubules (n = 1), meiotic arrest (n = 1) or mixed atrophy (n = 1) were enzymatically digested and dispersed cells were cultivated on 96-well plates or chamber dishes as aggregate-free cell suspensions. Time-lapse imaging of cluster formation was performed over a period of 48 h. For receptor tyrosine kinase inhibition of cluster formation, cells were treated twice with K252a within 2-3 days. Immunofluorescence staining and confocal microscopy was carried out on clusters after 1-3 weeks of cultivation to identify the presence of Sertoli cells (SC) (SOX9), peritubular myoid cells (SMA), Leydig cells (LC) (STAR), undifferentiated spermatogonia (FGFR3), differentiating spermatogonia/spermatocytes (DDX4) and postmeiotic germ cells (PRM1). Single clusters from four patients and a pool of eight larger clusters from another patient were manually picked and subjected to quantitative real-time PCR to evaluate the presence of SC (SOX9, AR), LC (INSL3, STAR, HSD3B1), peritubular myoid cells (ACTA2), fibroblasts (FSP1), endothelial cells (CD34), macrophages (CD68), undifferentiated spermatogonia (FGFR3), differentiating spermatogonia/spermatocytes (DDX4) and postmeiotic germ cells (PRM1). Finally, an ultrastructural investigation was conducted based on TEM of clusters from six different patients, among them 3-month cultivated large clusters from two patients.

MAIN RESULTS AND THE ROLE OF CHANCE

Quantitative PCR-based analysis of single-picked testicular cell clusters identified SC, peritubular myoid cells, endothelial cells, fibroblasts, macrophages, spermatids and LC after 1, 2 or 3 weeks or 3 months of cultivation. Immunofluorescence positivity for SC and peritubular myoid cells corroborated the presence of these two kinds of testis niche cells. In addition, round as well as elongated spermatids were frequently encountered in 1 and 2 weeks old clusters. Transmission electron microscopical classification confirmed all these cell types together with a few spermatogonia. Macrophages were found to be of the proinflammatory M1 subtype, as revealed by CD68+/CD163-/IL6+ expression. Time-lapse imaging uncovered the specific dynamics of cluster fusion and enlargement, which could be prevented by addition of protein kinase inhibitor K252a.

LARGE SCALE DATA

N/A.

LIMITATIONS REASON FOR CAUTION

Cell composition of the clusters varied based on the spermatogenic state of the TESE patient. Although spermatids could be observed with all applied methods, spermatogonia were only detected by TEM in single cases. Hence, a direct maintenance of these germ cell types by our system in its current state cannot be postulated. Moreover, putative dedifferentiation and malignant degeneration of cells in long-term cluster cultivation needs to be investigated in the future.

WIDER IMPLICATIONS OF THE FINDINGS

This work demonstrates that the reorganization of testicular cells can be achieved with TESE biopsies obtained from men enroled in a standard clinical assisted reproduction program. The formed clusters can be cultivated for at least 3 months and are composed, to a large extent, of the most important somatic cell types that are essential to support spermatogenesis. These findings may provide the cellular basis for advances in human in vitro spermatogenesis and/or the possibility for propagation of spermatogonia within a natural stem cell niche-like environment.

STUDY FUNDING AND COMPETING INTERESTS

The project was funded by a DFG grant to K.v.K. (KO 4769/2-1). The authors declare they have no conflicts of interest.

A testis-derived macroporous 3D scaffold as a platform for the generation of mouse testicular organoids

Extracellular matrix-derived scaffolds provide an efficient platform for the generation of organ-like structures.

Tissue Engineering to Improve Immature Testicular Tissue and Cell Transplantation Outcomes: One Step Closer to Fertility Restoration for Prepubertal Boys Exposed to Gonadotoxic Treatments

Despite their important contribution to the cure of both oncological and benign diseases, gonadotoxic therapies present the risk of a severe impairment of fertility. Sperm cryopreservation is not an option to preserve prepubertal boys’ reproductive potential, as their seminiferous tubules only contain spermatogonial stem cells (as diploid precursors of spermatozoa). Cryobanking of human immature testicular tissue (ITT) prior to gonadotoxic therapies is an accepted practice. Evaluation of cryopreserved ITT using xenotransplantation in nude mice showed the survival of a limited proportion of spermatogonia and their ability to proliferate and initiate differentiation. However, complete spermatogenesis could not be achieved in the mouse model. Loss of germ cells after ITT grafting points to the need to optimize the transplantation technique. Tissue engineering, a new branch of science that aims at improving cellular environment using scaffolds and molecules administration, might be an approach for further progress. In this review, after summarizing the lessons learned from human prepubertal testicular germ cells or tissue xenotransplantation experiments, we will focus on the benefits that might be gathered using bioengineering techniques to enhance transplantation outcomes by optimizing early tissue graft revascularization, protecting cells from toxic insults linked to ischemic injury and exploring strategies to promote cellular differentiation.

Testicular organoids: a new model to study the testicular microenvironment in vitro?

BACKGROUND

In recent decades, a broad range of strategies have been applied to model the testicular microenvironment in vitro. These models have been utilized to study testicular physiology and development. However, a system that allows investigations into testicular organogenesis and its impact in the spermatogonial stem-cell (SSC) niche in vitro has not been developed yet. Recently, the creation of tissue-specific organ-like structures called organoids has resurged, helping researchers to answer scientific questions that previous in vitro models could not help to elucidate. So far, a small number of publications have concerned the generation of testicular organoids and their application in the field of reproductive medicine and biology.

OBJECTIVE AND RATIONALE

Here, we aim to elucidate whether testicular organoids might be useful in answering current scientific questions about the regulation and function of the SSC niche as well as germ cell proliferation and differentiation, and whether or not the existing in vitro models are already sufficient to address them. Moreover, we would like to discuss how an organoid system can be a better solution to address these prominent scientific problems in our field, by the creation of a rationale parallel to those in other areas where organoid systems have been successfully utilized.

SEARCH METHODS

We comprehensively reviewed publications regarding testicular organoids and the methods that most closely led to the formation of these organ-like structures in vitro by searching for the following terms in both PubMed and the Web of Science database: testicular organoid, seminiferous tubule 3D culture, Sertoli cell 3D culture, testicular cord formation in vitro, testicular morphogenesis in vitro, germ cell 3D culture, in vitro spermatogenesis, testicular de novo morphogenesis, seminiferous tubule de novo morphogenesis, seminiferous tubule-like structures, testicular in vitro model and male germ cell niche in vitro, with no restrictions to any publishing year. The inclusion criteria were based on the relation with the main topic (i.e. testicular organoids, testicular- and seminiferous-like structures as in vitro models), methodology applied (i.e. in vitro culture, culture dimensions (2D, 3D), testicular cell suspension or fragments) and outcome of interest (i.e. organization in vitro). Publications about grafting of testicular tissue, germ-cell transplantation and female germ-cell culture were excluded.

OUTCOMES

The application of organoid systems is making its first steps in the field of reproductive medicine and biology. A restricted number of publications have reported and characterized testicular organoids and even fewer have denominated such structures by this method. However, we detected that a clear improvement in testicular cell reorganization is recognized when 3D culture conditions are utilized instead of 2D conditions. Depending on the scientific question, testicular organoids might offer a more appropriate in vitro model to investigate testicular development and physiology because of the easy manipulation of cell suspensions (inclusion or exclusion of a specific cell population), the fast reorganization of these structures and the controlled in vitro conditions, to the same extent as with other organoid strategies reported in other fields.

WIDER IMPLICATIONS

By way of appropriate research questions, we might use testicular organoids to deepen our basic understanding of testicular development and the SSC niche, leading to new methodologies for male infertility treatment.

RT-qPCR for PHOX2B mRNA is a highly specific and sensitive method to assess neuroblastoma minimal residual disease in testicular tissue

Neuroblastoma (NB) is the most common type of extracranial solid tumor in children with a high prevalence in toddlers. For childhood cancer survivors, preservation of reproductive potential is an important factor for quality of life. The optimization of NB minimal residual disease (MRD) detection in testicular tissue is crucial to evaluate the risk of malignant cell reintroduction. The first step in the present study was to assess the accuracy of reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to detect tyrosine hydroxylase (TH), paired-like homeobox 2b (PHOX2B) and doublecortin (DCX) mRNA expression in frozen/thawed testicular tissues of patients with non-obstructive azoospermia (NOA) contaminated (in vitro model) with an increasing number of IMR-32 and SK-N-SH NB cells. Testicular tissues were frozen by slow or snap freezing. The second step was to determine the expression levels of these markers in testicular samples from 4 pre-pubertal males (2 with stage IV NB and 2 with non-NB malignancy). The yield of extracted RNA was similar in testicular samples frozen by slow or snap freezing. In the in vitro model, TH and DCX transcripts were detected in uncontaminated testicular tissues, whereas PHOX2B mRNA was not detected. There was a strong positive association between the number of NB cells used for contamination and PHOX2B transcript levels. For IMR-32 and SK-N-SH NB cell lines, specificity and sensitivity rates of detection were 100% for PHOX2B following in vitro contamination with 10 tumor cells. In testicular samples from pre-pubertal males with and without NB, PHOX2B mRNA expression was not observed, but high expression levels of TH and DCX mRNA were detected, which were similar to expression detected in the in vitro model. Among the markers used in blood and bone marrow for NB MRD studies, the detection of PHOX2B transcripts by RT-qPCR may provide an accurate assessment of NB cells in testicular tissues from males who require fertility preservation.

Restoring Fertility with Cryopreserved Prepubertal Testicular Tissue: Perspectives with Hydrogel Encapsulation, Nanotechnology, and Bioengineered Scaffolds

New and improved oncological therapies are now able to cure more than 80% of cancer-affected children in Europe. However, such treatments are gonadotoxic and result in fertility issues, especially in boys who are not able to provide a sperm sample before starting chemo/radiotherapy because of their prepubertal state. For these boys, cryopreservation of immature testicular tissue (ITT) is the only available option, aiming to preserve spermatogonial stem cells (SSCs). Both slow-freezing and vitrification have been investigated to this end and are now applied in a clinical setting for SSC cryopreservation. Research now has to focus on methods that will allow fertility restoration. This review discusses different studies that have been conducted on ITT transplantation, including those using growth factor supplementation like free molecules, or tissue encapsulation with or without nanoparticles, as well as the possibility of developing a bioartificial testis that can be used for in vitro gamete production or in vivo transplantation.

Melatonin promotes development of haploid germ cells from early developing spermatogenic cells of Suffolk sheep under in vitro condition

Promotion of spermatogonial stem cell (SSC) differentiation into functional sperms under in vitro conditions is a great challenge for reproductive physiologists. In this study, we observed that melatonin (10(-7) M) supplementation significantly enhanced the cultured SSCs differentiation into haploid germ cells. This was confirmed by the expression of sperm special protein, acrosin. The rate of SSCs differentiation into sperm with melatonin supplementation was 11.85 ± 0.93% which was twofold higher than that in the control. The level of testosterone, the transcriptions of luteinizing hormone receptor (LHR), and the steroidogenic acute regulatory protein (StAR) were upregulated with melatonin treatment. At the early stage of SSCs culture, melatonin suppressed the level of cAMP, while at the later stage, it promoted cAMP production. The similar pattern was observed in testosterone content. Expressions for marker genes of meiosis anaphase, Dnmt3a, and Bcl-2 were upregulated by melatonin. In contrast, Bax expression was downregulated. Importantly, the in vitro-generated sperms were functional and they were capable to fertilize oocytes. These fertilized oocytes have successfully developed to the blastula stage.

Testicular biopsy and cryopreservation for fertility preservation of prepubertal boys with Klinefelter syndrome: a pro/con debate

In about one-half of adult Klinefelter syndrome (KS) patients, spermatozoa can be retrieved by means of testicular biopsy (TESE). Given the expected increase in the number of diagnosed KS patients owing to the use of noninvasive prenatal testing, the probable questions of young KS patients and their parents regarding future fertility, and the fact that widespread apoptosis of spermatogonia occurs at onset of puberty, an attempt to increase the retrieval rates at TESE above those found in adult KS men by undertaking preservation techniques peripubertally has been initiated. To date, however, only a limited number of KS adolescents have been examined, demonstrating no increases in the chances of finding sperm. Furthermore, spermatogonial stem cell and testicular tissue freezing techniques, as well as in vitro maturation strategies, require further validation. Given these controversies, banking testicular tissue from prepubertal KS boys should be performed only in a research framework.

Oncofertility: a grand collaboration between reproductive medicine and oncology

In 2007, I was asked by the University of Calgary to participate in a symposium called 'Pushing the Boundaries--Advances that Will Change the World in 20 Years'. My topic was oncofertility, a word I had just coined to describe the intersection of two disciplines--oncology and fertility--and I was thrilled to share my passion for this new field and help young women with cancer protect their future reproductive health. Fertility preservation in the cancer setting lacked a concerted effort to bridge the disciplines in an organized manner. In early 2015, I was delighted to deliver a presentation for the Society for Reproduction and Fertility titled 'Sex in Three Cities', where I gave an update on the oncofertility movement, a remarkable cross-disciplinary, global collaboration created to address the fertility preservation needs of young cancer patients. During my tour of the UK, I was impressed by the interest among the society and its members to engage colleagues outside the discipline as well as the public in a dialogue about cutting-edge reproductive science. In this invited review, I will describe the work of the Oncofertility Consortium to provide fertility preservation options in the cancer setting and accelerate the acceptance of this critical topic on a global scale. I hope that one day this word and field it created will change the world for women who had been left out of the equation for far too long.

Progress and prospects for fertility preservation in prepubertal boys with cancer

PURPOSE OF REVIEW

In the past few years, options for fertility preservation in prepubescent boys have enlarged tremendously.

RECENT FINDINGS

After a long period of studies on spermatogonial stem cell (SSC) transplantation in mice, recently successful use of rhesus monkey SSCs for autologous and allogeneic transplantation was demonstrated. Furthermore, newer protocols on transplantation of SSCs back into the testes and on how to mimic the niche environment have been described. Very importantly, a new multiparametric sorting strategy to eliminate cancer contamination from human testis cell suspension has been clarified.

SUMMARY

While awaiting for more data on safety issues, retrieval and cryopreservation of testicular tissue prior to cancer therapy should be offered, within an experimental context, to prepubertal boys with cancer who are at high risk of fertility loss.

Testicular function and fertility preservation after treatment for haematological cancer

PURPOSE OF REVIEW

Treatment for high-risk or relapsed haematological malignancy with haematopoietic stem cell transplantation is known to cause infertility. Today, there are no established options for fertility preservation in pre-pubertal boys. This review aims to describe how therapy for haematological malignancy in childhood affects male fertility, and to summarize recent developments for fertility preservation in these patients.

RECENT FINDINGS

Eventual recovery of spermatogenesis is probable after chemotherapy-based conditioning for haematopoietic stem cell transplantation. However, conditioning with total body irradiation is associated with a very high risk of permanent infertility. For high-risk patients, auto-transplantation of cryopreserved testicular tissue or cells might represent an approach for fertility preservation; however, contamination of testis tissue with malignant cells may prevent their subsequent reintroduction into patients. Recent progress using in-vitro differentiation of germ cells combined with assisted reproductive techniques may, in the future, represent a suitable alternative to retransplantation.

SUMMARY

Particular care must be taken when assessing infertility risk in patients with haematological malignancy as reclassification to high risk may significantly increase the likelihood of treatment-related gonadotoxicity. Importantly, development of fertility preservation strategies in such high-risk patients must also take into account specific risks for haematological cancers including cancer cell contamination.

Direct but no transgenerational effects of decitabine and vorinostat on male fertility

Establishment and maintenance of the correct epigenetic code is essential for a plethora of physiological pathways and disturbed epigenetic patterns can provoke severe consequences, e.g. tumour formation. In recent years, epigenetic drugs altering the epigenome of tumours actively have been developed for anti-cancer therapies. However, such drugs could potentially also affect other physiological pathways and systems in which intact epigenetic patterns are essential. Amongst those, male fertility is one of the most prominent. Consequently, we addressed possible direct effects of two epigenetic drugs, decitabine and vorinostat, on both, the male germ line and fertility. In addition, we checked for putative transgenerational epigenetic effects on the germ line of subsequent generations (F1-F3). Parental adult male C57Bl/6 mice were treated with either decitabine or vorinostat and analysed as well as three subsequent untreated generations derived from these males. Treatment directly affected several reproductive parameters as testis (decitabine & vorinostat) and epididymis weight, size of accessory sex glands (vorinostat), the height of the seminiferous epithelium and sperm concentration and morphology (decitabine). Furthermore, after decitabine administration, DNA methylation of a number of loci was altered in sperm. However, when analysing fertility of treated mice (fertilisation, litter size and sex ratio), no major effect of the selected epigenetic drugs on male fertility was detected. In subsequent generations (F1-F3 generations) only subtle changes on reproductive organs, sperm parameters and DNA methylation but no overall effect on fertility was observed. Consequently, in mice, decitabine and vorinostat neither affected male fertility per se nor caused marked transgenerational effects. We therefore suggest that both drugs do not induce major adverse effects-in terms of male fertility and transgenerational epigenetic inheritance-when used in anti-cancer-therapies.

Fertility preservation in men with cancer

During the past decade, advances in cancer treatment have increased survival rates of both boys and men. However, cancer treatment itself can compromise fertility, especially exposure to alkylating agents and whole body irradiation, which cause substantial germ cell loss. Children and adolescents with testicular cancer, leukaemia, and Ewing sarcomas are at the highest risk of developing permanent sterility from cancer treatment. Consequently, various strategies to preserve fertility are necessary. Sperm cryopreservation is an effective but underused method to safeguard spermatozoa. In the past few years, large advances have been made in prepubertal germ cell storage aimed at subsequent transplantation of testicular tissue and associated stem cells. Although still experimental, these approaches offer hope to many men in whom germ cell loss is associated with sterility. The derivation of male gametes from stem cells also holds much promise; however, data are only available in animals, and the use of this method in human beings is probably many years away.

Role of somatic cells on dairy processes and products: a review

Somatic cells are an important component naturally present in milk, and somatic cell count is used as an indicator of udder health and milk quality. The role of somatic cells in dairy processes and products is ill-defined in most studies because the role of these cells combines also the concomitance of physicochemical modifications of milk, bacterial count, and the udder inflammation in the presence of high somatic cell count. The aim of this review is to focus on the role of somatic cells themselves and of endogenous enzymes from somatic cells in milk, in dairy transformation processes, and in characteristics of final products overcoming biases due to other factors. The immune function of somatic cells in the udder defense and their protective role in milk will be primarily considered. Different characteristics of milk induced by various somatic cell counts, types, and their endogenous enzymes influencing directly the technological properties of milk and the final quality of dairy products will be discussed as well. By comparing methods used in other studies and eliminating biases due to other factors not considered in these studies, a new approach has been suggested to evaluate the effective role of somatic cells on dairy processes and products. In addition, this new approach allows the characterization of somatic cells and their endogenous enzymes and, in future research, will allow the clarification of mechanisms involved in the release of these components from somatic cells during dairy processes, particularly in cheese technologies.

In vitro Spermatogenesis - Optimal Culture Conditions for Testicular Cell Survival, Germ Cell Differentiation, and Steroidogenesis in Rats

Although three-dimensional testicular cell cultures have been demonstrated to mimic the organization of the testis in vivo and support spermatogenesis, the optimal culture conditions and requirements remain unknown. Therefore, utilizing an established three-dimensional cell culture system that promotes differentiation of pre-meiotic murine male germ cells as far as elongated spermatids, the present study was designed to test the influence of different culture media on germ cell differentiation, Leydig cell functionality, and overall cell survival. Single-cell suspensions prepared from 7-day-old rat testes and containing all the different types of testicular cells were cultured for as long as 31 days, with or without stimulation by gonadotropins. Leydig cell functionality was assessed on the basis of testosterone production and the expression of steroidogenic genes. Gonadotropins promoted overall cell survival regardless of the culture medium employed. Of the various media examined, the most pronounced expression of Star and Tspo, genes related to steroidogenesis, as well as the greatest production of testosterone was attained with Dulbecco's modified eagle medium + glutamine. Although direct promotion of germ cell maturation by the cell culture medium could not be observed, morphological evaluation in combination with immunohistochemical staining revealed unfavorable organization of tubules formed de novo in the three-dimensional culture, allowing differentiation to the stage of pachytene spermatocytes. Further differentiation could not be observed, probably due to migration of germ cells out of the cell colonies and the consequent lack of support from Sertoli cells. In conclusion, the observations reported here show that in three-dimensional cultures, containing all types of rat testicular cells, the nature of the medium per se exerts a direct influence on the functionality of the rat Leydig cells, but not on germ cell differentiation, due to the lack of proper organization of the Sertoli cells.